Gauge Invariance in Field Theory and Statistical Physics in Operator Formalism

TL;DR

This paper derives Ward identities and gauge-dependence of Green's functions in non-Abelian gauge theories using operator formalism, and introduces a gauge-invariant statistical averaging method applicable to theories with spontaneous symmetry breaking.

Contribution

It provides a novel operator-based derivation of gauge identities and defines a generalized statistical average ensuring gauge-invariant Green's functions in complex gauge theories.

Findings

Derived Ward identities using canonical commutation relations.

Defined a gauge-invariant statistical averaging procedure.

Applicable to theories with and without spontaneous symmetry breaking.

Abstract

We obtain the Ward identities and the gauge-dependence of Green's functions in non-Abelian gauge theories by using only the canonical commutation relations and the equations of motion for the Heisenberg operators. The consideration is applicable to theories both with and without spontaneous symmetry breaking. We present a definition of a generalized statistical average which ensures that the Fourier images of temperature Green's functions of the Fermionic fields have only even-valued frequencies. This makes it possible to set up a procedure of gauge-invariant statistical averaging in terms of the Hamiltonian and the field operators.